• Nucleotidase converts AMP to adenosine
• Adenosine deaminase converts adenosine to inosine and free ammonium
• Nucleotide phosphorylase converts inosine to hypoxanthine
• Xanthine oxidase converts hypoxanthine to xanthine

Introduces a keto group

Xanthine is a common intermediate in the breakdown of GMP and AMP

Xanthine oxidase introduces another ketone group in hypoxanthine to make xanthine

• Xanthine oxidase converts xanthine into uric acid and H2O2

Adds another ketone group

• Uric acid is deprotonated under physiological conditions to be urate

This is where it stops for humans, birds, and reptiles

We’ve lost the uricase gene so we can’t do urate -> allantoin

• Uric acid can be broken down in 2 steps to be allantoin (uricase)

Can be released in urine by squirrels

Further catabolism can lead to NH3 fish